U.S. patent number 10,237,916 [Application Number 14/871,518] was granted by the patent office on 2019-03-19 for systems and methods for esc temperature control.
This patent grant is currently assigned to Tokyo Electron Limited. The grantee listed for this patent is Tokyo Electron Limited. Invention is credited to Alok Ranjan, Sergey A. Voronin.
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United States Patent |
10,237,916 |
Voronin , et al. |
March 19, 2019 |
Systems and methods for ESC temperature control
Abstract
This disclosure relates to a temperature control system that may
be used in a plasma processing system that treats microelectronic
substrates using plasma. The temperature control system may include
a heating array disposed adjacent to the microelectronic substrate
and that may selectively generate heat at different portions of the
microelectronic substrate. The heating array may include heating
modules that selectively generate heat depending upon a breakover
voltage of a Silicon Diode for Alternating Current (SIDAC). The
amount of heat generated heat may depend upon the resistance of the
heating module and the duty cycle of the variable voltage
signal.
Inventors: |
Voronin; Sergey A. (Delmar,
NY), Ranjan; Alok (Mechanicville, NY) |
Applicant: |
Name |
City |
State |
Country |
Type |
Tokyo Electron Limited |
Tokyo |
N/A |
JP |
|
|
Assignee: |
Tokyo Electron Limited (Tokyo,
JP)
|
Family
ID: |
58407731 |
Appl.
No.: |
14/871,518 |
Filed: |
September 30, 2015 |
Prior Publication Data
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Document
Identifier |
Publication Date |
|
US 20170094719 A1 |
Mar 30, 2017 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01J
37/32082 (20130101); H01L 21/67103 (20130101); H01J
37/32724 (20130101); H01J 37/32009 (20130101); H05B
1/0233 (20130101); H01L 21/67248 (20130101) |
Current International
Class: |
H05B
1/02 (20060101); H01L 21/67 (20060101); H01J
37/32 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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102668058 |
|
Sep 2012 |
|
CN |
|
2015-520504 |
|
Jul 2015 |
|
JP |
|
M370189 |
|
Dec 2009 |
|
TW |
|
Other References
Combined Office Action and Search Report dated May 16, 2018 in
Taiwanese Patent Application No. 105131181 (with English language
translation) citing references AO--AQ therein, 13 pages. cited by
applicant.
|
Primary Examiner: Fuqua; Shawntina
Attorney, Agent or Firm: Oblon, McClelland, Maier &
Neustadt, L.L.P.
Claims
What is claimed is:
1. An apparatus, comprising: a signal generator that generates a
power modulation signal; a heating array coupled to the signal
generator, the heating array comprising heating modules that are
arranged in parallel, the heating modules comprising a load element
and a switch element that are in electrical communication with the
signal generator, the load element being in series with the switch
element; a substrate chuck adjacent to the heating array, the
substrate chuck comprising a supporting surface for a
microelectronic substrate; and an electrostatic chuck component
that can generate an electromagnetic field, the electrostatic chuck
component being subjacent to the substrate chuck.
2. The apparatus of claim 1, wherein at least two of the load
elements comprise different resistance values and the switching
elements comprise different breakover voltages.
3. The apparatus of claim 1, wherein the switching elements
comprise thyristor devices or bi-directional diodes.
4. The apparatus of claim 1, wherein the signal generator comprises
a voltage component that varies voltage and duty cycle.
5. The apparatus of claim 4, wherein a first group of heating
modules comprises breakover voltages within a first range; and a
second group of heating modules comprising breakover voltages
within a second range that is different from the first range.
6. The apparatus of claim 1, wherein the heating array comprises a
first group of heating modules comprising breakover voltages within
a first range; and a second group of heating modules comprising
breakover voltages within a second range that is different from the
first range.
7. An apparatus, comprising: a substrate support surface that can
support a microelectronic substrate; a heating array subjacent to
the substrate support surface, the heating array comprising a first
parallel arrangement of heating elements, the heating elements
comprising a load element connected in series with a bi-directional
current component; and an electrostatic chuck component subjacent
to the substrate support surface.
8. The apparatus of claim 7, wherein the heating array comprises a
second parallel arrangement of heating elements that are in series
with the first parallel arrangement of heating elements that is in
parallel with at least one diode.
9. The apparatus of claim 7, wherein the bi-directional current
components comprise different breakover voltages.
10. The apparatus of claim 9, wherein the load elements comprise
different resistance values.
11. The apparatus of claim 9, wherein the load elements comprise a
common resistance value.
12. The apparatus of claim 9, wherein the load elements comprise
two or more groups of the load elements that have different
resistance values.
13. The apparatus of claim 7, wherein the heating elements
comprises two or more groups of the bi-directional current
components that have different breakover voltages.
14. The apparatus of claim 7, wherein the bi-directional current
components comprise an electrical element that conducts current
flow when a first voltage is applied and prevents current flow
through the electrical element when a second voltage is
applied.
15. The apparatus of claim 7, further comprising a single power
source coupled to the heating array.
16. A method for treating a substrate, comprising: receiving a
microelectronic substrate on a substrate holder comprising an
electrostatic chuck and a parallel arrangement of heating elements
comprising a load element in series with a switch element; applying
a chucking voltage to the electrostatic chuck; applying a variable
voltage signal to the parallel arrangement to achieve a first
temperature profile across the substrate holder; and heating
portions of the substrate holder based, at least in part, on the
variable voltage and the load elements.
17. The method of claim 16, wherein the variable voltage signal
comprises a bi-polar component.
18. The method of claim 16, wherein the heating further comprises
changing the variable voltage signal to obtain a second temperature
profile across the substrate holder.
19. The method of claim 16, wherein the heating is further based,
at least in part, on breakover voltages of the load elements.
20. The method of claim 16, wherein the heating is further based,
at least in part, on a duty cycle of the variable voltage.
Description
FIELD OF THE DISCLOSURE
This invention relates to semiconductor processing technology, and
more particularly, to systems and methods for controlling
temperature of a microelectronic substrate during plasma
treatments.
BACKGROUND
The geometries of microelectronic features continue to scale to
smaller sizes and increase in complexity. Accordingly, the
processing techniques used to manufacture microelectronic devices
may need to become more precise to create smaller features on
microelectronic substrates. Further, the size of microelectronic
substrates may also increase over time. Plasma processing may be
used to form or etch features on the microelectronic substrate.
Plasma treatments may be influenced by many different process
conditions, but substrate temperature may play an important role
when forming features, in a uniform manner, across the
microelectronic substrate. Although existing plasma systems may use
heating elements within substrate chucks, they may lack the ability
to finely control temperature across microelectronic substrates to
form smaller features in a cost effective manner. Accordingly,
improving temperature resolution for substrate chucks in a cost
effective manner may be desirable.
SUMMARY
This disclosure relates to systems and methods for controlling
temperature during treatments of microelectronic substrates used to
manufacture microelectronic devices. A wide variety of
semiconductor processing techniques may be influenced by the
temperature of the microelectronic substrate. The processing
techniques may include, but are not limited to, etching,
deposition, curing and the like. Temperature control may include
applying energy (e.g., heat) to portions of the microelectronic
substrate to achieve a steady-state or a temperature profile across
the surface of the microelectronic substrate. However, improving
the temperature resolution over smaller portions of the
microelectronic substrate may be problematic, in that scaling
existing systems to include more power sources and heating elements
that may be in closer proximity to each other may increase cost and
system complexity. The increased cost may arise from adding
additional power sources and the hardware/software infrastructure
to manage the additional power sources in a cooperative manner.
Disclosed herein are systems and methods that may minimize tool
cost by using heating elements that may be individually controlled
using a single power source.
In one embodiment, the system may include a process chamber that
may treat microelectronic substrates with plasma. The process
chamber may be in electrical or fluid communication with several
system components that may deliver gases, energy, or vacuum that
may be used to generate plasma. Additionally, the process chamber
may include a substrate holder that may be used to heat the
microelectronic substrate during plasma processing. The substrate
holder may include a supporting surface that may secure the
microelectronic substrate using an electrostatic coupling
component. In one specific instance, the substrate holder may also
include a heating array that may be used to selectively heat
different portions of the microelectronic substrate. The heating
array may include heating modules that may be arranged across the
substrate holder that may be used to selectively heat the
microelectronic substrate. The heating modules may be arranged in
parallel, such that a single power source can apply a voltage to
all of the heating modules. The heating array may receive a power
modulation signal or variable voltage signal that may be
selectively applied to the load elements (e.g., resistors) based,
at least in part, on the configuration of the corresponding switch
element (e.g., thyristor or bi-directional diode). In this
instance, the switch elements may be configured with different
trigger voltages or breakover voltages that may allow current to
reach the corresponding load element under certain conditions. The
current may drive the heat generation, via the resistor, that is
transferred to the microelectronic substrate. A signal generator or
power source may vary the voltage and duty cycle of the pulse
modulated signal to selectively breakover switches. For example,
portions of the heating array may selectively receive current at
specific heating modules based, at least in part, on the switch
element breakover design and the design of the variable voltage
signal. In this way, a person of ordinary skill in the art may
generate a pulse modulated signal that targets designated heating
modules to maintain a desired temperature profile across the
microelectronic substrate.
In one embodiment, the switch elements may be assigned to different
groups that may allow different portions of the substrate holder to
be heated. For example, the heating array may have a first group of
heating modules comprising the same or similar breakover voltages
and a second group of heating modules may have different breakover
voltages from the first group. The substrate may selectively heat
the microelectronic substrate using the first group without using
the second group of heating modules. However, the variable voltage
signal may shift, in such a way, that heating may be done by using
the first and second group at the same time. For example, the first
group may have breakover voltages within a first range, such that
the first group may be used for heating using a first power
modulation signal provided by the signal generator. The first power
modulation signal may trigger the breakover of the switch elements
causing current to flow through the load elements that may generate
heat that may be transferred to the substrate or plasma. A second
power modulation signal may be configured to trigger the switch
breakover for the first group and a second group of heating
modules. In another embodiment, the second power modulation signal
may trigger switch breakover for the second group and not the first
group of switching elements. In this way, the power signal
modulation signals and the switch elements may be optimized to
selectively heat the substrate based, at least in part, on the
location of the heating modules with respect to the substrate.
Hence, the heating module placement, power modulation signals,
switching element breakover voltages, and load element resistances
may be optimized to achieve different temperature profiles that may
be optimized to alter plasma etching/deposition performance on the
microelectronic substrate.
In another embodiment, a heating array may be disposed subjacent to
the microelectronic substrate support surface and may include a
parallel arrangement heating elements. The heating elements may be
arranged in parallel geometrically, electrically or both. The
heating array may be electrically coupled to a single power signal
generator that may provide a varying voltage signal that may be
used to selectively apply current to different portions of the
heating array. Selectively applying current to portions of the
heating array may enable different substrate temperature profiles
during plasma treatments. A person of ordinary skill in the art may
optimize the heating array design and the voltage signal
modulations to obtain different temperature profiles to address
process non-uniformity across the microelectronic substrate. The
heating array may be disposed above or below an electrostatic
coupling component that may be used to secure (e.g., magnetically)
the microelectronic substrate to the support surface.
In this embodiment, the heating array may include heating elements
that may include a load element (e.g., resistor) and a
bi-directional current component (e.g., thyristor) to regulate when
current may be applied to the load element. The bi-directional
current components may be designed with specific breakover voltages
that may switch between a passive state that may prevent current
from flowing through the bi-directional current component to the
load element. When the breakover voltage, applied by the signal
generator, exceeds a threshold amount, the bi-directional component
may transition to an active state and allow current flow through to
the respective load element. In one specific embodiment, the
bi-directional current component may include a silicon diode for
alternating current (SIDAC) that may transition between the
aforementioned passive state and active state.
In another specific embodiment, the bi-directional current
components may comprise different breakover voltages that may allow
a person of ordinary skill in the art to direct current flow to a
specific element or to a subset of load elements. The amount of
heating may be related to the current magnitude and the resistance
of the load element(s). In one instance, the load elements may have
the same or similar resistance values and may the same or similar
amount of heat. However, in other embodiments, the load elements
may have different resistance values and may generate different
amounts of heat, even if the same or similar current or voltage may
be applied to the load elements. In this instance, the heating
array may include two or more groups of heating elements that may
have common breakover voltages that may allow the selective
application of current to their respective load elements. Also, the
groups of heating elements may have different resistances, such
that portions of the groups may generate differing amounts of heat
using the same applied voltage. Over time, the selective current
application may generate a temperature profile across the
microelectronic substrate.
In certain embodiments, the heating array may include a temperature
feedback system that may optimize the power modulation signal to
maintain certain temperature conditions across the microelectronic
substrate. For example, this may include higher temperatures at the
edge of the microelectronic substrate than at the center. In other
embodiments, the temperature profile may have a center-high and
edge-low temperature profile.
One method for obtaining a temperature profile across the
microelectronic substrate may include receiving the microelectronic
substrate on a substrate holder of a plasma processing chamber. The
substrate holder may also include an holder that may be used to
magnetically secure microelectronic substrate to substrate holder.
In this embodiment, the substrate holder may include an arrangement
of heating elements that may include a load element and a switching
element placed in series with each other. The heating elements may
form a circuit in which the heating elements are in parallel with
each other, such that each heating element may receive the same
voltage at then respective switching elements. The heating elements
may be used to form a temperature profile across the
microelectronic substrate, by selectively heating portions of the
substrate holder to counter heat loss/gain during plasma
processing. In this instance, a controller for the plasma system
may apply a variable voltage signal to the parallel arrangement of
the heating elements. A first portion of the switch elements may
exceed their breakover voltages and allow current to flow through
to their respective load elements. Accordingly, the load elements
(e.g., resistors) may increase in temperature based, at least in
part, on the amount of current, duty cycle and the resistance
magnitude of the load elements. The heating may form a first
temperature profile along the substrate chuck. In other
embodiments, the first temperature profile may transition to a
second temperature profile based on changes in the variable voltage
signal that may increase or decrease the amount of heating elements
that may be in active state. In other embodiments, the second
temperature profile may be enabled by using the same heating
elements, but varying the amount of current that may be provided to
the load elements. For example, the breakover voltage may be
maintained for the second voltage variable, but the magnitude of
the signal may be lower or higher to decrease or increase the
amount of heat generated at the load elements.
This summary is intended to provide an overview of the disclosure
and is not intended to limit the scope of the claims to embodiments
described above. The embodiments described in the summary are
merely for illustrative purposes.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are incorporated in and constitute
a part of this specification, illustrate embodiments of the
invention and, together with a general description of the invention
given above, and the detailed description given below, serve to
explain the invention. Additionally, the left most digit(s) of a
reference number identifies the drawing in which the reference
number first appears.
FIG. 1 is an illustration of a representative embodiment of a
plasma processing system that shows a schematic cross-sectional
illustration of a plasma chamber that may include a heating array
disposed in a substrate holder according to at least one
embodiment.
FIG. 2 is an illustration of a circuit diagram of the heating array
according to at least one embodiment.
FIG. 3 is an illustration of a representative embodiment of power
modulation signal that may be applied to the heating array
according to at least one embodiment.
FIG. 4 is an illustration of another circuit diagram of the heating
array according to at least one embodiment.
FIG. 5 is an illustration of another representative embodiment of
the power modulation signal that may be applied to the heating
array according to at least one embodiment.
FIG. 6 is a flow diagram for method for generating temperature
profiles for a microelectronic substrate using the heating array
according to at least one embodiment.
DETAILED DESCRIPTION
The following Detailed Description refers to accompanying drawings
to illustrate exemplary embodiments consistent with the present
disclosure. References in the Detailed Description to "one
embodiment," "an embodiment," "an exemplary embodiment," etc.,
indicate that the exemplary embodiment described can include a
particular feature, structure, or characteristic, but every
exemplary embodiment does not necessarily include the particular
feature, structure, or characteristic. Moreover, such phrases are
not necessarily referring to the same embodiment. Further, when a
particular feature, structure, or characteristic is described in
connection with an embodiment, it is within the knowledge of those
skilled in the relevant art(s) to affect such feature, structure,
or characteristic in connection with other exemplary embodiments
whether or not explicitly described.
"Substrate" or "Microelectronic substrate" as used herein
generically refers to the object being processed in accordance with
the embodiments described herein. The microelectronic substrate may
include any material portion or structure of a device, particularly
a semiconductor or other electronics device, and may, for example,
be a base substrate structure, such as a semiconductor substrate or
a layer on or overlying a base substrate structure such as a thin
film. Thus, substrate is not intended to be limited to any
particular base structure, underlying layer or overlying layer,
patterned or unpatterned, but rather, is contemplated to include
any such layer or base structure, and any combination of layers
and/or base structures. The description below may reference
particular types of substrates, but this is for illustrative
purposes only and not limitation.
The exemplary embodiments described herein are provided for
illustrative purposes, and are not limiting. Other embodiments are
possible, and modifications can be made to exemplary embodiments
within the scope of the present disclosure. Therefore, the Detailed
Description is not meant to limit the present disclosure. Rather,
the scope of the present disclosure is defined only in accordance
with the following claims and their equivalents.
The following Detailed Description of the exemplary embodiments
will so fully reveal the general nature of the present disclosure
that others can, by applying knowledge of those skilled in the
relevant art(s), readily modify and/or adapt for various
applications such exemplary embodiments, without undue
experimentation, without departing from the scope of the present
disclosure. Therefore, such adaptations and modifications are
intended to be within the meaning and plurality of equivalents of
the exemplary embodiments based upon the teaching and guidance
presented herein. It is to be understood that the phraseology or
terminology herein is for the purpose of description and not
limitation, such that the terminology or phraseology of the present
specification is to be interpreted by those skilled in relevant
art(s) in light of the teachings herein.
FIG. 1 depicts a plasma processing system 100 for treating
substrates using plasma (not shown) that may be generated in a
plasma chamber 102. Plasma may be generated by applying
electromagnetic energy (e.g., power sources 106) to a process
gas(es) that is provided by a gas delivery system 104 to the plasma
chamber 102. The gas delivery system 104 may include mass flow
controllers, check valves, and the like to be used control gas
mixture distribution. A vacuum system 108 in fluid communication
with the plasma chamber 102 may also maintain a sub-atmospheric
pressure during plasma generation. The vacuum system 108 may
include one or more pumps and control systems (e.g., N.sub.2
ballast system, butter-fly valve system) to control the pressure
within the plasma chamber 102.
Plasma generation may be done by applying electromagnetic energy to
an electrically neutral gas to cause electrons to be released from
a gas molecules that are positively charged (e.g., ion) as result
of the lost electron. The ions may be characterized as a molecule
or atom where the total number of electrons are not equal to the
total number of protons resulting in a positive charge. Molecular
or atomic radicals (e.g., molecules or atoms with at least one
unpaired electron) may also be generated from the electrically
neutral gas. Generally, the radicals may have a neutral, positive,
or negative charge and may have high chemical reactivity relative
to the ions. Over time, the electromagnetic energy and the
increasing electron collisions within the gas mixture may increase
the density of ionized molecules and radicals within the gas
mixture that may be used to treat the substrate 110.
The plasma chamber system 100 may alter certain process conditions
to influence the amount of flow of ions and/or radicals towards the
substrate, such that the ionized molecules (not shown) may be
influenced by potential differences within the plasma chamber 102.
For example, the potential differences within the plasma chamber
102 may direct the ionized molecules (or atoms, or radicals)
towards a substrate 110. The ions and radicals may interact with
the substrate 110 or treat the substrate through deposition or
passivation or that may remove a portion of the substrate.
In FIG. 1, the plasma chamber 102 cross section illustration 112
illustrates one embodiment of the plasma chamber 102 that includes
a power source assembly 114 that enables the transmission of
electromagnetic energy (e.g., microwave energy, RF energy) and the
gas mixture (not shown) into the region proximate to the substrate
110. The gas mixture may be introduced into the plasma processing
region 116 that is proximate to the substrate holder 124, along the
gas pathway 120 through the center of the power source assembly
114. In other embodiments, the gas mixture may be introduced from
other locations within the plasma chamber 102. The plasma
processing region 116 may also receive energy from a first energy
source 122 to generate plasma that may be used to treat a substrate
110 disposed on the substrate holder 124. The electromagnetic
energy may include electromagnetic energy (e.g., microwave energy
@>300 MHz and/or radio-frequency (RF) energy @<300 MHz) that
may transmitted, in some way, from the power source 106 to the
power source assembly 114. In the FIG. 1 embodiment, the power
source assembly 114 may include a microwave waveguide 126 and the
dielectric component 128 may be disposed around the gas pathway
118.
The gas mixture in the plasma processing region 116 may also
receive electromagnetic energy from a second source (e.g., bias
power source 130) that may bias the substrate holder 124 and
influence the plasma characteristics proximate to the substrate
110. In some embodiments, the bias power source 130 and the first
power source 122 may be operated in unison or alone to generate
plasma within the plasma processing region 116. In addition to
electromagnetic energy, plasma characteristics may also be
influenced by temperature, particularly close to the substrate 110.
The temperature profile across the substrate 110 may be influenced
by heat loss to the chamber walls or heat gain from the plasma.
These heat sources and/or heat sinks may impact processing
temperature at the substrate 110 that may cause process
non-uniformities (e.g., etch rate, deposition rate, etc.) across
the substrate 110. One approach to control the temperature profile
may be to include a heating array 132 that may include heat sources
(not shown) distributed underneath the substrate 110. The heating
array 132 may selectively apply heat to the substrate 110 to alter
the temperature profile to reduce process non-uniformities. The
heat sources (not shown) may generate heat when a signal generator
142 applies an electrical signal to one or more portions of the
heating array 132. The biasing of the substrate holder 124, the
power assembly 114 and the heating array 132 may be implemented by
using a controller 134 that may coordinate the process sequencing
that generates plasma within the plasma processing region 116.
The controller 132 may use a computer processor 136 and memory 138
to execute computer-readable instructions that may be provided over
an electrical communication network 140 to control the plasma
processing system 100 components (e.g., power sources 106, gas
delivery 104, etc.). The one or more computer processors 136 may
include, without limitation: a central processing unit (CPU), a
digital signal processor (DSP), a reduced instruction set computer
(RISC), a complex instruction set computer (CISC), a
microprocessor, a microcontroller, a field programmable gate array
(FPGA), or any combination thereof. The memory 136 may include one
or more computer-readable storage media ("CRSM"). In some
embodiments, the one or more memories may include non-transitory
media such as random access memory ("RAM"), flash RAM, solid state
media, and so forth. Broadly, the controller 134 may control the
sequencing of processing events that enable plasma generation or to
transition between different types of plasma that may be exposed to
the substrate 110.
The plasma processing system 100 may be used to implement several
different types of plasma that may be used to etch patterns into
the substrate 110, deposit films onto the substrate 110 or to dope
the substrate 110. As the size and complexity of electronic devices
increases, the need for higher precision processing uniformly
distributed across the substrate 110 has increased. In some plasma
processing embodiments, the temperature profile across the
substrate 110 may have strong impact on etch rates, deposition
rates, or doping concentrations across the substrate 110. For
example, having different etch rates at the center and edge of the
substrate 110 may cause different amounts of the substrate 110 to
be removed. This uneven removal may impact feature size or
geometry, such that devices at different locations on the substrate
110 may operate differently from one another or some portions of
the devices may not operate properly, if at all. A person of
ordinary skill in the art may use the controller 134 to select
regions of the substrate 110 that may be heated by the heating
array 132 to minimize the plasma process non-uniformities across
the substrate 110. The controller 134 may operate the heating array
132 in a closed loop or open loop manner.
FIG. 2 is an illustration of a circuit diagram 200 of one
embodiment of the heating array 132 that may be disposed in the
substrate holder 124. The heating array 132 may include a plurality
of heating modules 202 that may be arranged in parallel with each
other, such that any input signal or applied voltage to a common
terminal 204 may be concurrently applied to the plurality of
heating modules 202 Although FIG. 2 illustrates four heating
modules 202, 202a, 202b, 202c other embodiments may include up to
nth number of heating modules 202. The heating module(s) 202 may be
used to generate heat that may be transferred to the substrate
holder 124 and/or the substrate 110.
The heating modules 202, 202a, 202b, 202c may include switch
elements 210, 210a, 210b, 210c and may be disposed in series with
their respective load element 208, 208a, 208b, 208c. The heating
module 202 may be regulated between active state (e.g., generating
heat) or a passive state (e.g., no heating) by controlling the
current flow to the load elements 208. The switch elements 210,
210a, 210b, 210c may prevent or enable current flow to or from the
load elements 208, 208a, 208b, 208c. The switch element 210 may be
a bi-directional current component that allows current flow through
the switch element 210 after a threshold voltage is exceeded. For
example, the bi-directional component may be arranged to allow
current to flow through them when a voltage threshold is exceeded.
In one specific embodiment, the bi-directional component may be a
thyristor that may include four layers that alternate between
different dopant conditions (e.g., n-type or p-type) that may
operate as a bistable switch that transitions to a conductive state
when a voltage threshold is exceeded. For example, if the voltage
threshold was 5V and the signal generator provides an electrical
signal that is less than 5V, the switch element 210 may not allow
current to flow through to the load element 208. However, when the
electrical signal applied to the common terminal 204 exceeds 5V,
the switch element 210 may allow current to flow through to the
load element 208 that may generate heat that may be transferred to
the substrate holder 124 and/or the substrate 110. Accordingly, the
current flow to the load elements 208, 208a, 208b, 208c may be
controlled based, at least in part, on the threshold voltages of
their corresponding switch elements 210, 210a, 210b, 210c and the
type of signal provided by the signal generator 142. Several
different embodiments of heating module 202 arrangements, load
element 208 types and switch element 210 types may be used to
generate different temperature profiles at the substrate 110.
In one embodiment, the heating modules 202 may be evenly
distributed across the substrate holder 124. The load elements may
have the same or similar resistance values and the threshold
voltages for the switch elements 210 may be the same or similar for
all the heating modules 202. In this instance, the heating modules
202 may generate the same or similar amount of heat when the
electrical signal from the signal generator 142 may be applied to
the heating array 132. In this embodiment, the switch elements 210,
210a, 210b, 210c may transition to an active state at the same time
and allow the same or similar amount of current to be applied to
the load elements 208, 208a, 208b, 208c. The heating modules 202
may generate the same amount of heat to the substrate holder
124.
However, in some embodiments, the temperature profile across the
substrate 110 may not be uniform due to heat loss and/or gain
inherent in the process chamber 102 and the plasma process. For
example, the center of the substrate holder 124 may more easily
retain heat than the perimeter of the substrate holder 124. The
higher heat loss at the edge may be driven due to geometrical
peculiarities of the substrate holder, its edge area may be more
effectively cooled by process cooling water, etc. In this instance,
the edge of the substrate holder 124 may have a higher heat loss
and may make the edge of the substrate holder 124 cooler than the
center of the substrate holder 124, in this specific
embodiment.
In other embodiments, the heating array 132 may include any number
of heating modules 202 that may be disposed within or adjacent to
the substrate holder 124. The heating modules 202 may be
distributed across the substrate holder 124, such that each heating
module 202 may be responsible for heating specific zones underneath
the substrate 110. The heating zones may or may not overlap each
other, depending upon the temperature profile needed for a specific
process. The heating zones may also overlap depending on the
characteristics of the heating modules 202, 202a, 202b, 202c, such
that the response times, settling times, and overshoot control of
the heating modules may vary from process to process. The heating
module 202 may include a switch element 210 and a load element 208
that may be connected in series with each other. The heating
modules 202a, 202b, 202c may be arranged in parallel to each other,
such that each heating module 202, 202a, 202b, 202c may receive the
same electrical signal from the signal generator. However, the
switch elements 210, 210a, 210b, 210c may have different threshold
voltages, such that a portion the switch elements (e.g., 210, 210a)
may flow current to their respective load elements (e.g., 208,
208a) while the remaining switch elements (e.g., 210b, 210c) may
not flow current to their respective load elements (e.g., 208b,
208c). In this way, the heating modules 202, 202a, 202b, 202c may
be used to selectively heat portions of the substrate holder 124 at
different times and/or at different intensities.
The heating modules 202, 202a, 202b, 202c, 202n.sup.th may be
arranged by groups throughout the substrate holder 124 to cover
zones or regions of the substrate 110. For example, the center
region of the substrate 202 by a first group (not shown) of heating
modules 202 and edge region of the substrate 110 may be covered by
a second group (not shown) of heating modules 202. In this way, the
heating modules 202 may be able to generate heat in a selective
manner across or around the substrate holder 124. The selective
heating may be depend upon the location of the heating modules 202
and how they may be arranged with respect to each other and their
relative heating performance. The heating performance or
temperature profile across the substrate 110 may be based, at least
in part, on the resistance of the load elements 208, the threshold
voltages of the switch elements 210, and the voltage and/or duty
cycle of electrical signal applied to the heating modules 202.
In one embodiment, the heating modules 202 of the first group and
the second group may be co-located with at least one heating module
202 from the other group. The two heating modules 202 that are
proximate to each other may have different threshold voltages for
their switch elements 210 and they may have different resistances
for their load elements 208. In this instance, the paired heating
modules 202 may cover the same or similar zone, but may heat the
zone differently based, at least in part, on different load
elements 208 and the magnitude of the current provided to the load
elements 208. In this way, the heating modules 202 may be designed
to generate heat in a different manner based on how the different
load elements 208 react to the signal applied by the signal
generator 142. These factors may result in different temperature
magnitudes, ramp times, settling times, or temperature overshoot.
Another aspect of the heating array 132 may be the use of a single
signal generator 142 to power all of the load elements 208 through
the common terminal 204. Using a single signal generator 142 may
reduce the cost of the plasma processing system 100 and reduce the
cost of maintenance.
FIG. 3 is an illustration of one embodiment an electrical signal
300 or power modulation signal that may be generated by the signal
generator 142 and applied to the heating array 132. The electrical
signal 300 may be designed to generate a uniform temperature
profile across the substrate chuck 124. However, the temperature
profile may not be required to be uniform and the electrical signal
300 may be designed generate to higher or lower temperatures at
selected portions of the heating array 132. As noted above, the
different heat transfer characteristics of the plasma chamber 102
may cause temperature changes across the substrate 110 that may
warrant a less uniform or non-uniform temperature profile across
the substrate chuck 124 using the heating array 132. For example,
in one specific instance, ion and electric currents from the plasma
may increase the temperature at a higher rate or value at the
center of the substrate chuck 124. Hence, it may be desirable to
limit the amount of heat generated by the heating array 132 at the
center of the substrate chuck 124. This may be accomplished by
designing an electrical signal 300 that accounts for the threshold
voltages and resistances of the heating modules 202 to reduce the
amount of heat generated by the heating modules 202 proximate to
the center of the substrate 124. However, the temperature profile
across the substrate chuck 124 may also be impacted by conditions
other than plasma. Likewise, the electrical signal 300 may be
designed to apply more energy to other heating modules 202 that may
have a lower temperature than the center of the substrate 124. For
example, the edge or perimeter of the substrate chuck 124 may have
higher heat loss that may impact the uniformity of the plasma
treatment across the substrate 110. Accordingly, the electrical
signal 300 may be designed to apply more energy to the heating
modules 202 at the edge of the substrate chuck 124 to increase
process uniformity across the substrate 110. A person of ordinary
skill in the art may be able to program the controller 134 to
enable the signal generator 142 to selectively target heating
modules 202 to achieve desired plasma process results.
The signal generator 142 may be any device that may generate a
repeating or non-repeating electronic signal (analog or digital)
that may vary in voltage and duty cycle (e.g., pulse duration and
period). The electrical signal 300 may be designed to selectively
exceed the threshold voltages for selected switch elements 210 for
discrete periods of time to allow current to flow to their
respective load element 208, which generate heat. The amount of
heat generated by the load element may depend upon, but is not
limited to, load element 208 resistance, switch element 210
threshold voltage, and the duty cycle.
The duty cycle may be a ratio of the duration of time a threshold
voltage may be applied and the period of the electrical signal 300
that oscillates between the "on" and "off" state the heating module
202. The duty cycle may be varied to apply voltage to different
heating modules 202 for different periods of time. In this way, a
person of ordinary skill in the art may adjust the temperature
profile by applying different voltages for different periods of
time to select heating modules 202. In this way, differences in
heat retention or flux throughout the substrate holder 124 or
plasma chamber 102 may be compensated for by the heating array 132
to generate a desired temperature profile during the plasma
treatment.
Turing to FIG. 3, one embodiment of the electrical signal 300 may
be represented by a Voltage (U(t)) vs time (.tau.) graph that
illustrates when and how much voltage may be applied to the heating
array 132. The signal generator 142 may vary the voltage between
two or more threshold voltages (e.g., first voltage 302, second
voltage 304, third voltage 306, . . . n voltage 308) for discrete
periods of time (e.g., first time 310, second time 312, third time
314, . . . n time 316). For example, the first voltage 302 may be
the threshold voltage for first switch element 210a, the second
voltage 304 may be the threshold voltage for the second switch
element 210b, and the third voltage 306 may be the threshold
voltage for the third switch element 210c. In this instance, the
voltages may be cumulative, in that when the second voltage 304 is
applied to the heating array 132, the first load element 208a and
the second load element 208b may generate power. However, the
second load element 208b may generate power during the second time
312 period, but the first load element 208a may generate power
during the first time 310 period and the second time 312 period.
Likewise, during the third time 314 period, all three load elements
208a, 208b, 208 may generate power (e.g., heat) during that time.
In one embodiment, the electrical signal 300 may repeat through the
same conditions again or the electrical signal 300 may be modified
to power the heat modules 202 in a different way. Accordingly, a
person of ordinary skill in the art may modify the electrical
signal 300 to generate power or heat at particular locations across
the heating array 132 by varying the threshold voltage and duty
cycle of the electrical signal 300. Table 1 illustrates several
embodiments of electrical signal 300 variation.
TABLE-US-00001 TABLE 1 Settings A: T1 < T2 < T3 B: T1 < T3
< T2 C: T3 < T2 < T1 R1 400 Ohm U1 85 V U1 80 V U1 88 V R2
80 Ohm U2 100 V U2 100 V U2 115 V R3 22 Ohm U3 210 V U3 210 V U3
210 V Uth1 5 V Duty1 0.7 Duty1 0.75 Duty1 0.85 Uth2 90 V Duty2 0.1
Duty2 0.12 Duty2 0.08 Uth3 200 V Duty3 0.01 Duty3 0.009 Duty3 0.008
P1 16 W P1 16 W P1 20 W P2 18 W P2 20 W P2 18 W P3 20 W P3 18 W P3
16 W Settings D: T2 < T3 < T1 E: T1 << T2 << T3
F: T3 << T2 << T1 R1 400 Ohm U1 88 V U1 85 V U1 88 V R2
80 Ohm U2 110 V U2 100 V U2 110 V R3 22 Ohm U3 210 V U3 210 V U3
210 V Uth1 5 V Duty1 0.85 Duty1 0.1 Duty1 0.91 Uth2 90 V Duty2 0.07
Duty2 0.05 Duty2 0.07 Uth3 200 V Duty3 0.01 Duty3 0.01 Duty3 0.002
P1 20 W P1 4 W P1 20 W P2 16 W P2 12 W P2 12 W P3 18 W P3 20 W P3 4
W
Table 1 illustrates six embodiments of how the electrical signal
300 may be varied to provide power to different heating modules 202
in the same heating array 132. As shown under the settings column,
the load elements 208 resistance and switch elements 210 threshold
voltages are presumed not to vary. In this instance, the load
elements 208a, 208b, 208c may have a resistance varying from
400.OMEGA. down to 22.OMEGA. and the switch elements 210a, 210b,
210c may have threshold voltages varying from 5V to 200V. However,
in other embodiments, the resistances and threshold voltages are
not required to be fixed values. But, the fixed settings may be
able to produce different temperature profiles by varying the
voltage and the duty cycle of the electrical signal 300. This may
be preferable to switching out components from the heating array
132. Columns A-F of Table 1 provide representative embodiments of
how a single heating array 132 may be used to obtain different
temperatures at different locations using the same load elements
208.
Column A, of Table 1, illustrates a desired temperature profile
(e.g., T1<T2<T3) where the temperature at first load element
208a is less than the temperature of the second load element 208b
and the third load element 208c and the temperature of the third
load element 208c is greater than the temperature of the second
load element 208b. In this embodiment, the first voltage 302 may be
about 85V for a duty cycle of 0.7, which means that the first
voltage 302 may be applied for about 70% of the period of the
electrical signal 300. Next, the electrical signal 300 may increase
to 100V with a duty cycle of about 0.1. In this instance, the first
load element 208a and the second load 208b may generate power
during this portion or time period. Lastly, the electrical signal
300 may transition to 210V for a duty cycle of 0.01. The electrical
signal 300 of column A may repeat as needed to achieve the desired
temperature profile across the substrate chuck 124. In this
embodiment, the first load element 208a may generate 16 W or a
lower temperature than the second load element 208b (e.g., 18 W)
and the third load element 208c (e.g., 20 W). The power may be
determined using equation (1) described below in the description of
FIG. 6.
The column B embodiment illustrates another desired temperature
profile (e.g., T1<T3<T2) using the same heating array 132
that may be used to implement the column A embodiment. In this
instance, the voltages may be similar to the column A embodiment,
but the duty cycle of the column B embodiment varies slightly from
the column A embodiment. For example, the first voltage 302 may be
about 85V for a duty cycle of 0.75, which means that the first
voltage 302 may be applied for about 75% of the period of the
electrical signal 300. Next, the electrical signal 300 may increase
to 100V with a duty cycle of about 0.12. In this instance, the
first load element 208a and the second load 208b may generate power
during this portion. Lastly, the electrical signal 300 may
transition to 210V for a duty cycle of 0.009. In this embodiment,
the first load element 208a may generate 16 W or a lower
temperature than the second load element 208b (e.g., 18 W) and the
third load element 208c (e.g., 20 W), but the second load element
208b (20 W) generates a higher temperature than the third load
element 208c(e.g., 18 W). As noted above, the power may be
determined using equation (1) described below in the description of
FIG. 6.
The column C embodiments illustrates another desired temperature
profile (e.g., T3<T2<T1) using the same heating array 132
described in the column A embodiment. For example, the first
voltage 302 may be about 88V for a duty cycle of 0.85, which means
that the first voltage 302 may be applied for about 85% of the
period of the electrical signal 300. Next, the electrical signal
300 may increase to 115V with a duty cycle of about 0.08. In this
instance, the first load element 208a and the second load 208b may
generate power during this portion. Lastly, the electrical signal
300 may transition to 210V for a duty cycle of 0.008. In this
embodiment, the first load element 208a may generate 16 W or a
lower temperature than the second load element 208b (e.g., 18 W)
and the third load element 208c (e.g., 20 W), but the second load
element 208b (20 W) generates a higher temperature than the third
load element 208c (e.g., 18 W). As noted above, the power may be
determined using equation (1) described below in the description of
FIG. 6.
The embodiments illustrated in columns D, E, F provide additional
examples of how the temperature profile across the substrate may be
varied by making changes to the electrical signal 300, particularly
the voltage magnitude and the duty cycle.
FIG. 4 is an illustration of another circuit diagram 400 of the
heating array 132 that increases (e.g., may double) the amount of
heating modules 202 from the FIG. 2 embodiment. In this instance,
another row of heating modules 402 may be placed in series with the
heating modules 202 from FIG. 2. The heating modules 402 may
contain a switch element 404 connected in series with a load
element 406 and may be in parallel with another signal regulation
component 206, 408 (e.g., diode). Again, the electrical signal 300
may be applied across the common terminals 204, such that each of
the electrical signal 300 may be applied to each group of heating
modules (e.g., 202, 402). In the FIG. 4 embodiment, the circuit
diagram 400 includes eight heating modules 202, 202a, 202b, 202c,
402, 402a, 402b, 402c, but other embodiments may not be limited to
eight and may include many more heating modules (e.g., 202, 402)
than shown in FIG. 4.
Increasing the amount of heating modules 202, 402 in the heating
array 132 may enable a higher degree of temperature control
resolution. For example, if the surface area of the substrate chuck
124 surface area in the FIG. 2 embodiment is also used with the
FIG. 4 heating array 132, the higher density of the heat sources
may increase the temperature control resolution. The higher heat
source density may increase the ability to adjust or to obtain a
desired temperature profile due when each heat source may be used
to control temperature over a smaller surface area. Having a higher
density of heat sources make allow a person of ordinary skill in
the art to control the temperature profile to a tighter tolerance
or reduce temperature variation across the substrate chuck 124. The
higher heat source density may also reduce temperature variation by
placing the heat source closer to each other so that they may
collaborate to manage transient temperature conditions,
particularly temperature transient conditions in high thermal flux
regions (e.g., substrate chuck perimeter) where temperature
variation may be harder to stabilize or control.
Although adding heat modules 402 may increase temperature control,
the heating array 132 may still receive the same or similar
electrical signal from one or more signal generators (not shown).
However, in one specific embodiment, the FIG. 4 heating array 132
may still be powered by a single generator 142 using a bi-polar
power signal to accommodate the additional heating modules 402.
FIG. 5 includes an illustration of a graphic-representation of a
bi-polar electrical signal 500 or power modulation signal that may
be applied to the FIG. 4 heating array 132 to generate desirable
temperature profiles across the substrate chuck 124. FIG. 5 merely
illustrates one embodiment of the bi-polar electrical signal 500.
In other embodiments, a person of ordinary skill in the art may be
able to design other bi-polar electrical signals (not shown),
similar to the Table 1 embodiments, to achieve a variety of
different temperature profiles across the substrate chuck 124.
The bi-polar electrical signal 500 may turn on or off individual or
groups of heating modules 202, 402 by using positive or negative
voltage values that are applied for discrete periods of time. The
individual heating modules (e.g., 202, 402) or groups of heating
modules (e.g., 202a, 202b, 202c) may have different breakover
voltages from the remaining heating modules (e.g., 402a, 402b,
402c). Likewise, the remaining heating modules (e.g., 402a, 402b,
402c) may also have different breakover voltages from each other,
as shown in FIG. 5. However, they are not required to have
different breakover voltages.
As shown in FIG. 5, the bi-polar electrical signal 500 may have
voltage variations as a function of time (e.g., U(t)) that may
alternate between a positive voltage regime and a negative voltage
regime. In contrast to FIG. 3 embodiment, the FIG. 5 embodiment
utilizes the negative voltage regime to enable the ability to
selectively target additional heating sources without having to
increase the number of heating sources 202, 402 that will be active
at the same time. For example, in Table 1 column A the using a
negative voltage regime may allow additional heat modules 402 to be
active (e.g., applied negative voltage) while the positive voltage
regime heat modules 202 (in column A) may be turned off. Hence, the
bi-polar electrical signal 500 may increase the selectivity of how
many heat modules 202, 402 may be turned on or off. Using the
positive and negative voltage regime, in combination with the duty
cycle and different threshold voltages for the switch elements 210,
404, may increase the amount of heating modules 202, 402 (as shown
in FIG. 4) that may be individually controlled using the one power
signal generator 142. Accordingly, the FIG. 4 heat array 132
embodiment may have a higher temperature resolution than the FIG. 2
embodiment.
In the FIG. 5 embodiment, the bi-polar electrical signal 500 may
alternate between positive voltages U1n 502 (e.g., U11 504, U12
506, U13 508) for discrete periods of time .tau.1n 510 (e.g.,
.tau.11 510, .tau.12 512, .tau.13 514) and negative voltages U2n
516 (e.g., U21 518, U22 520, U23 522) for discrete periods .tau.2n
524 (e.g., .tau.21 526, .tau.22 528, .tau.23 530) of time that may
vary depending upon the desired duty cycle or temperature profile
across the substrate 110. The FIG. 5 embodiment is provided merely
for illustrative purposes and the scope of the disclosure is not
intended to be limited to this embodiment. A person of ordinary
skill in the art may vary the voltage and duty cycle to enable a
plurality of temperature profiles as described in the Table 1
embodiments. For example, in one embodiment, the first array of
heating modules 202 may be arranged around the edge of the
substrate chuck 124 and the second array of heating modules 402 may
be arranged closer to the center of the substrate chuck 124. In
this instance, a person of ordinary skill in the art may vary the
duty cycle to apply more power to one or more of the first array of
heating modules 202 because the edge of the substrate chuck 124 may
have a higher heat flux than the center of the substrate chuck 124.
The higher heat flux, in one instance, may be due to the edge of
the substrate being closer to the cooler process chamber 102 wall.
Hence, the temperature profile may vary across the substrate 110
and the duty cycle and voltage of the bi-polar electrical signal
500 may be varied to minimize temperature uniformity across the
substrate 110.
However, in other embodiments, a person of ordinary skill in the
art may use the heating array 132 to induce temperature
non-uniformity across the substrate 110. The temperature
non-uniformity may be used to increase reaction rates (e.g.,
deposition or etch) at different positions of the substrate 110. In
one embodiment, the localized temperature variation may be used to
account for variations in the substrate 110 that may include, but
are not limited to, thickness variations or feature size variations
across the substrate 110. For example, the substrate 110 may
include have a higher film thickness at the edge of the substrate
110 that at the center of the substrate 110. Hence, having the same
etch rate at the center of the substrate 110 may not remove enough
of the film at the edge of the substrate. Incomplete removal of the
film across the substrate 110 may be detrimental to the quality or
yield of the devices being manufactured on the substrate 110. A
person of ordinary skill in the art may vary the duty cycle and
voltage to selectively apply power to each of the heating modules
202, 402 by using the bi-polar electrical signal 500 may increase
the amount of heating modules 202, 402 that may be used to generate
temperature profiles across the substrate 110. The variation of the
bi-polar electrical signal 500 may be similar to the embodiments of
Table 1, except for the increase in the number of resistive
elements and the negative voltage set points that may enable a
higher degree of control over the individual heating modules 202,
402.
In one bi-polar electrical signal 500 embodiment, the signal
regulation components 206, 408 direct the current towards first
array of heating modules 202 or second array of heating modules
402, depending on the configuration of the signal regulation
components 206, 408. In the FIG. 4 embodiment, the signal
regulation components 408 may be a diode that has a breakover
voltage that may be greater than the voltage provided by the power
signal generator 142. When a positive voltage is applied to the
circuit diagram 400, the current flows through the second signal
regulation component 408 which directs the current towards the
first array of heating modules 202. Due to a small voltage drop
across diode 408, there is minimum or zero current flowing through
the second array of heating modules 402. when a negative voltage is
applied to the circuit 400, the signal regulation components
206,408 may direct the current to the second set of heating modules
402 and may not subject the first set of heating modules 202 to the
applied voltage from the power signal generator 142. The switch
elements 404 may be configured to selectively apply the bi-polar
electrical signal 500 based, at least in part, on the difference in
breakover voltages of the switch elements 404. Hence, the heating
modules 404 may selectively heat the substrate chuck in a similar
manner as shown in Table 1, but with a combination of positive and
negative voltages and different duty cycles to account for the
additional elements not shown in Table 1. In this way, a person of
ordinary skill in the art may selectively generate heat across the
substrate 110 by selectively applying power to the load elements
208, 406 based, at least in part, on the combination of the duty
cycle, signal voltage, and the breakover voltages of the switching
elements 210, 404.
FIG. 6 is a flow diagram 600 for a method for generating
temperature profiles across the microelectronic substrate 110 using
the heating array 132 during a plasma processing treatment. The
method of FIG. 6 illustrates one embodiment for using the heating
array 132 and other steps may be added or omitted to achieve a
desired result as determined by a person of ordinary skill in the
art of plasma processing. In one embodiment, the heating array 132
may include heating modules 202 distributed across the substrate
chuck 124. The heating array 132 may include a combination of a
switching elements 210 and load elements 208. The switching
elements 210 may designed to pass current to its respective load
element 208 at specific voltages, as shown in Table 1. The load
elements 208 may generate heat depending upon the amount of current
that may be received from the power signal generator 142 and the
load element 208 resistance, as shown in Table 1. The duty cycle
and power signal voltage may be varied as shown in FIGS. 3 and 5 to
selectively generate heat using the heating modules 202, 402 for
discrete periods of time.
Turning now to FIG. 6, at block 602, the plasma treatment process
may begin when a microelectronic substrate 110 may be placed on a
substrate holder (e.g., substrate cuck 124) that may include an
electrostatic chuck or component that may be used to secure the
substrate 110 in the plasma chamber 102. The electrostatic chuck
may or may not be separate from the heating array 132 that may
include a parallel arrangement of heating elements (heating modules
202) that may be used to generate heat at localized portions of the
substrate 110 or be used in combination to generate a temperature
profile across the substrate 110.
At block 604, the electrostatic chuck may generate an electrostatic
potential subjacent to the substrate 110 that may be used to clamp
or secure the substrate 110 to prevent movement during the plasma
treatment. The electrostatic chuck may receive a chucking voltage
from chucking power source that may be operated independently of
the power signal generator 142. However, the chucking voltage may
be applied to the substrate chuck 124 when the heating array 132
may be receiving a signal from the power signal generator 142.
Following the application of the chucking voltage, the plasma
process treatment may begin or the plasma process treatment may
begin after a desired temperature profile may be established across
the substrate 110 prior to the plasma treatment. In another
embodiment, the electrostatic chucking may be not be used. Hence,
block 604 may be omitted from the FIG. 6 method in this
instance.
At block 606, the temperature profile may be generated by applying
a variable voltage signal to the parallel arrangement (e.g.,
heating array 132) to achieve a first temperature profile across
the substrate chuck 124. The variable voltage signal may be similar
to the signals illustrated in FIGS. 3 & 5 or described in Table
1. In the FIG. 3 embodiment, the variable voltage signal may vary
between different positive voltage set points for discrete periods
of time. The varying voltage may be used to select which heating
module 202 that may be used to generate heat at different locations
across the substrate 110. The duty cycle may determine how long the
varying voltage may be held constant to enable an individual
heating module(s) 202 to generate heat. At the end of the time
period, the voltage may change to a different voltage set point,
such that a different or another heating module 202 may be exposed
to the voltage. As noted above in the descriptions of FIGS. 2-5,
the voltage exposure may be dependent upon the threshold voltage of
the switching element 210 of the targeted heating module 202. If
the voltage exposure is greater than the threshold voltage the
voltage may be applied to the load element 208 to generate heat for
that discrete period. Again, at the end of that time period, the
voltage may change to another voltage set point for another period
of time and use a different heating module 202 to generate heat for
another discrete period of time.
In another embodiment, the variable voltage signal may be the
bi-polar electrical signal 500 that may incorporate a positive
voltage component and a negative voltage component. As noted in the
description of FIG. 5, the bi-polar electrical signal 500 vary
between positive negative voltages to selectively target a specific
switch elements 404 or group of switch elements 404a, 404b. Again
the bi-polar electrical signal 500, may be applied for discrete
periods of time to target specific heating modules 402.
At block 608, portions of the substrate holder (e.g., substrate
chuck 124) may be selectively heated based, at least in part, on
the variable voltage, duty cycle and the load elements. More
particularly, the heating array 132 within the substrate holder may
generate a temperature profile across the substrate 110. The
heating array 132 may selectively heat portions of the substrate
110 by arranging heating modules 202 at different positions within
the substrate holder. The heating module 202 may include the switch
elements (e.g., switch elements 210, 210a, etc.) that may prevent
or allow current to reach their respective resistors (e.g., load
elements 208, 208a, etc.) that generate the heat.
As noted in the description of FIGS. 2-5, the variable voltage
signal may include a voltage signal that may vary with time to
selectively target specific heating modules 202 or groups of
heating modules 202, 202a to generate heat for discrete periods of
time or a desired duty cycle. For example, Table 1 illustrates one
embodiment of a heating array 132 that includes three heating
modules 202 that includes three load elements 208 (e.g., R1, R2,
R3) and their corresponding switch elements 210 (e.g., Uth1, Uth2,
Uth3). The load elements 208 may receive current when the variable
voltage signal exceeds the threshold values for Uth1, Uth2, Uth3,
such that R1 may receive current when the variable voltage signal
has a voltage greater than 5V, and R1 and R2 may receive current
when the variable voltage signal has a voltage greater than 90V,
and that R1, R2, and R3 may receive current when the variable
voltage signal has a voltage greater than 200V.
However, the amount of time the load elements 208 may be exposed to
current may also depend upon the duty cycle of the variable voltage
signal. As shown in Table 1, R1 may be exposed to current for about
70% of the time, R2 may be exposed to current for about 1% of the
time, and R3 may be exposed to current for about 0.1% of the signal
period. A person of ordinary skill in the art may arrange the duty
cycle, such that the amount of time that R1, R2, and R3 are exposed
to the current may not exceed 100%. In this embodiment, R1 may
generate approximately 16 W of power, R2 may generate approximately
18 W of power, and R3 may generate approximately 20 W of power. The
power may be determined by using equation (1):
P.sub.n=[U.sub.1.sup.2D.sub.1+U.sub.2.sup.2D.sub.2+ . . .
U.sub.n.sup.2D.sub.n]/R.sub.n (1)
In other embodiments, a person of ordinary skill in the art may
also select the amount of heating modules 202 and their arrangement
across the substrate holder 124 to achieve a desired temperature
profile. Further, the variable voltage signal may be designed to
assist in maintaining the temperature profile across the substrate
110. In this way, the heating array 132 may achieve different
temperature profiles using the same heating modules 202 in the
substrate holder. A person of ordinary skill in the art may vary
the duty cycle to generate different heating conditions due to the
variance in power, as shown in Table 1, where the power generated
by each of the load elements 208 (e.g., R1, R2, R3) may vary in
power between 4 W and 20 W based, at least in part, on the duty
cycle. Hence, a person of ordinary skill in the art would configure
the duty cycle to achieve the desired power levels at load elements
208 (e.g., R1, R2, R3) or the desired temperature profile across
the substrate 110.
It is to be appreciated that the Detailed Description section, and
not the Abstract section, is intended to be used to interpret the
claims. The Abstract section can set forth one or more, but not all
exemplary embodiments, of the present disclosure, and thus, is not
intended to limit the present disclosure and the appended claims in
any way.
While the present disclosure has been illustrated by the
description of one or more embodiments thereof, and while the
embodiments have been described in considerable detail, they are
not intended to restrict or in any way limit the scope of the
appended claims to such detail. Additional advantages and
modifications will readily appear to those skilled in art. The
invention in its broader aspects is therefore not limited to the
specific details, representative apparatus and method and
illustrative examples shown and described. Accordingly, departures
may be made from such details without departing from the scope of
the general inventive concept.
* * * * *